Electroplating barrel



June 14, 1966 E. o. NElLsoN ELECTROPLATING BARREL 2 Sheets-Sheet 1 Filed May 25, 1964 INV EN TOR. L/lzllfafz June 14, 1966 E. o. NElLsoN 3,255,170

ELECTROPLATING BARREL Filed May 25, 1964 2 Sheets-Sheet a Z INVENTOR. i@ ZZ/77%)" miam?,

56 y @w/fg@ United States `Patent O 3,256,170 i ELECTROPLATING BARREL Elmer 0. NeilsonNorth Lake, Ill., assignor to Mercxl Plating Equipment Company, Chicago, Ill., a corporation of Iliinois Filed May 25, 1964, Ser. No. 371,168 11 Claims. (Cl. 204-213) This application is a continuation-impart of my copending application, Serial No. 36,196 which was iiled lune 15, 1960, and which is now abandoned.

This invention relates generally to electroplating apparatus and especially to electroplating apparatus of the kind adapted to handle batches of small parts.

In one specific aspect, the present invention relates to a button-type electroplating barrel.

Metal parts are frequently provided with an electrolytically deposited coating of such materials as nickel, copper and cadmium in order to reduce corrosion and improve appearance; and according to modern practice,

small metal parts are electroplated employing drums or barrels which are adapted to contain individual batches of parts and which are adapted to be rotated while immersed in an electroplating bath. These barrels generally are of either the dangler-type or the button-type in compliance with the method of making electrical connection to the parts being electroplated.

In the button-type barrel, the staves or ribs ofthe barrel comprise an elongated electrically insulative member which surrounds a metal rod or bar, usually of copper or brass, the metal rod or bar being connected to a source of power. 'Ihe button contacts extend through the insulative member into electrical connection with lthe metal bar.

Heretofore, button-type electroplating barrels have been restricted to the use of certain materials in their construction because of the corrosive action of plating solutions and because of the diiliculties encountered in establishing and maintaining a fluid-tight electrical path to the button contacts. Specifically, the chemical resistance of such materials as hard rubber, polypropylene and methyl methacrylate polymers has been unavailable in button-type barrels due to the problems involved in molding either of these materials around a metal insert 'in the fabrication of barrel components.

Therefore, an important object of the present invention is to provide a new and improved electroplating barrel of the button-type.

.A further object of the invention is to provide an electroplating barrel construction which permits use of polymeric materials having a coeiiicient of thermal contraction which dilers substantially from that of the metal inserts so as to preclude successful-molding of such material about the inserts.

A .more specific object of the invention is to provide a button-type electroplating barrel incorporating ribs and end iianges fabricated Vfrom a methyl methacrylate polymer.

Another object of the invention is to provide a buttontype electroplating barrel incorporating ribs and end llanges vfabricated from hard rubber.

Yet `another object ofthe invention is to provide a button-type electroplating barrel incorporating ribs and end anges fabricated Ifrom polypropylene.

Still another object of the invention is to provide a button-type electroplating barrel which is resistant to electroplating solutions and which provides a fluid-tight electrical path to its contents.

Yet another object of the invention is to provide a button-type electroplating barrel which is characterized by ease and economyof fabrication.

Patented June 14, 1966 lCe Additional objects and features of the invention pertain to t-he particular structure, materials and arrangements whereby the above objects are attained.

A structure in accord with the invention includes a pair of electrically insulative end ilanges arranged to be synchronously rotated in spaced relationshipone of the end anges being'fonmed with a Amachined recess adapted to receive an electricallyV conductive spider, the spider being connected to a source of power and the recess being closed by means of a cooperatively shaped plate sealed over the spider with an adhesive; a plurality of ribs extending between the ilanges in peripheral locations, each of the ribs including an elongated electn'cally insulative member having a longitudinal groove therein, a conductive bar electrically connected to the spider and received in the groove, and a cooperatively shaped member closing the groove by being sealed over the bar; a plurality of perforated panels fastened between adjacent ribs; and a plurality of electrically conductive button-type contact means extending radially through each of the ribs in fluid-tight relationship to enl gage the conductive bar, so constructed and arranged that the structure is resistant to electroplating solutions and provides a fluid-tight electrical path to the contents of the barrel.

The invention, both to its structure and mode of operation, will be better understood by reference to the following disclosure and drawings forming a part thereof, wherein:

FIG. 1 is a perspective view or a button-type electroplating barrel constructed in accordance with the invention;

FIG. 2 is an enlarged, vertical, cross-sectional View of the barrel of FIG. l taken in end elevation;

FIG. 3 is an enlarged view taken through the section 3-3 of FIG. 1;

FIG. 4 is an enlarged View taken through the section 44 or FIG. 2;

FIG. 5 is an enlarged View taken through the section 5 5 of FIG. 4; and.

FIG. 6 is an enlarged perspective view showing the end of one of the ribs employed in the barrel of FIG. 1.

Referring now in detail to the drawings, specifically -to FIG. l, a button-type electroplating barrel indicated genassembly 12 and a live hanger assembly 14; A hanger channel 16 is advantageously xed between the assemblies 12 and 14 above the Ibarrel 10 for purposes of sup-` porting the barrel 10 in an electroplating tank in compliance with well-known practice. For purposes of implementing the rotation of barrel 10, a spur gear 18 is secured to a drive flange or head 20; and a pinion gear 22 meshes with spur gear 18 delivering motive power thereto from an appropriate source.

Spaced apart from and arranged to be synchronously rotated with drive flange 20 is a live flange or head 24. A number of ribs or staves 26 extend between the flanges 20 and 24 in equally arcuately spaced, peripheral locations. With reference for the moment to FIG. 3, a rib 26 will be seen provided with longitudinally extending, angulated slots 28 emanating from its opposite sides; and into these slots 28 are inserted panels 30.

Returning now to FIG. l1, the panels 30 will -be seen perforated with numerous holes in order to allow free circulation of the electroplating fluids through the barrel; and as is -best shown in FIG. 2, the panels 30 extend between adjacent ribs 26 deiining all but one of the sides of the barrel 10. The remaining side of the barrel is closed 0 by -means of a panel 32 which is fashioned with tapered With reference to FIG. 1, panel 32 is advantageously provided with handles 34 and with suitable clamp means 36 used `for securing the plate 32 in place. As will be recognized, batches of small parts to be electroplated may be easily loaded and unloaded from the barrel 1G by means of the removable panel 32; and while the holes in the several panels 30 and in the panel 32 provide ready communication of the electroplating solutions to the contents of the barrel, these holes are advantageously arranged to be of such a size as to prevent the contents of the barrel from sifting out into the electroplating tank.

Referring now to FIG. 4, the live hanger assembly 14 will 'be seen to include a hanger arm 38 having an electrically conductive element 40 enclosed therein as by being molded therein as an insert. Element 4S is preferably fabricated from bronze and terminates in a hanger arm bushing 42. Hanger arm 38, on the other hand, is ar- `ranged to be electrically insulative and is fabricated from either a melamine resin-linen laminate or methacrylic resin. A hollow cylindrical ltrunnion bushing 44 is received in the hanger arm bushing 42 and is adapted to receive a trunnion 46 which may be desirably `fabricated from steel.

The trunnion 46 is employed in rotatably mounting the live end flange 24 to the hanger assembly 14 and for providing a portion of the electrical path as will be described vmore 4fully hereinafter. Cooperating with the trunnion 46 in the horizontally rotatable mounting of flange 24 is a hanger arm flange bushing 48, a`flange bushing t) and a flange cover 52. Bushing 48 is desirably fabricated from a chemically resistant rubber whereas bushing 5G is desirbaly fabricated from a melamine resin-linen laminate; Cover 52 is made from a methyl methacrylate resin. Trunnion 46 terminates in a mounting flange 54 which is secured to the flange 24 as by means of screws 56. The cover 52 is fastened to flange 24 by means of screws 58.

The flange 24 is adapted to encase an electrically conductive spider 60 which is desirably made of bronze and which defines a portion of the electrical path between trunnion 46 and the several ribs 26. In accordance with a feature of the present invention, spider 6i) is set into a recess 62 which is milled into the flange 24. The recess 62 is closed by means of a cooperatively shaped plate 64 which -issealed over the spider with a suitable adhesive applied 'between abutting surfaces of the cover 64 and the main body of the llange 24 or by the creation of a fusion joint between these abutting surfaces.

As will be noted from an inspection of FIG. 4, plate 64 is interposed between cover 52 and mounting flange 54. Moreover, a stud 66 threadedly engages both the spider 60 and the trunnion 46. Adjacent the ends of the several arms of spider 60, flange 24 -is fashioned with longitudinally extending bores 6S which terminate at the spider 60. Into each bore 68 is thrust the turned end 70 of a rib 26, as is shown in FIG. 4.

Each rib 26 contains an electrically conductive bar 72 preferably fabricated from brass; and this 'bar 72 is arranged to abut the arm of spider 60, a screw 74 advantageously extending through the arm of spider 60 to threadedly engage bar 72 for purposes of establishingand maintaining intimate contact. A resinous plastic plug 76 is desirably secured over the head of screw 74 as by -threadedly engaging the plate 64; and a washer 78 is usefully interposed between the head of plug 76 and plate 64. Furthermore, a rubber washer 80 is positioned in an annular grove 82 formed in the end of rib 26 in order to seal off the connection of spider 60 and bar 72.

In accordance with an important feature of the invention, bar 72 is incorporated in rib 26 by milling a longitudinal groove 84 in the rib, inserting the bar 72 in the groove 84 and closing off the groove by adhesively sealing a cooperatively shaped member 86 over the bar, the adhesive being applied between abutting surfaces of rib 26 and the member 86. This arrangement of the rib means of the invention is well shown in FIGS. 3-5. The member 86 may also be secured in place by forming a fusion joint with the abutting surfaces of rib 26.

Completing the electrical path is a number of button contacts S8 which are advantageously fashioned from chrome plated, low carbon steel and which pass through apertures 90 in the ribs S6 to engage bar 72 threadedly. A block 92, desirably formed of a phenolic resin-linen laminate, is disposed between the head of each contact 88 and the surface of the corresponding rib 26.

As has become apparent from the foregoing descriptions, the live end flange 24 and the rib means 26 are arranged in such a manner as to avoid the necessity of employing molding in order to establish a fluid-tight enclosure for spider 60 and bar 72. Accordingly, the flange 24 and the rib means 26 are selected to be fabricated from materials displaying good chemical resistance but heretofore excluded from button-type electroplating barrel construction by virtue of their possessing a coelllcient of thermal contraction which differs substantially from that of the metal inserts and which therefore establishes incompatibility with being molded successfully about a metal insert. Specifically, flange 24 and rib means 26 are selected to be fabricated from hard rubber when relatively high operating temperatures on the order of 225 F. are to be employed and when resistance to caustic solutions is desired. Furthermore, these members are arranged to be fabricated from methyl methacrylate polymers when operating temperatures not materially exceeding 180 F. are anticipated and when superior resistance to either caustic or acidic solutions is desired. In addition, flange 24 and rib means 26 are arranged to be made from polypropylene polymeric material where operating temperatures in the range of -212 F. are expected and resistance to rough handling is required.

When the flange 24 and the rib means 26 are selected to be fabricated fromy hard rubber, the plate 64 and the member 36 are also selected to be fabricated from the same material. Furthermore, the adhesive to be employed in securing the plate 64 and the member 86 in the flange 24 .and the rib means 26 respectively is, under such circumstances, selected to be a compatible adhesive, such as the adhesive sold by the Armstrong Cork Company of Lancaster, Pennsylvania, under the trade name of Armstrong A-l Cement.

In similar manner, when the flange 24 and the rib means 26 are selected to be fabricated from a methyl methacrylate polymer, the plate 64 and the member 86 are selected to be fabricated from the same material. Under these circumstances, the adhesive to be employed is selected to be a solvent solution of the methyl methacrylate polymer; and in one specific embodiment of the invention, the solvent employed has been 'ethylene dichloride. Other adhesive mixtures may be employed.

When the flange 24, the rib means 26, the plate 64 and the member 86 are selected to be fabricated from polypropylene resinous material, the connections between abutting surfaces are advantageously made by heating the .assembled parts to incipient melting while holding the parts under a suitable clamping pressure. A fusion joint is produced. Other heat welded connections can be made.

It is to be recognized that other elements of the barrel 10 are desirably fabricated from appropriate materials. For example, when ribs 26 and end flange 24 are fabricated from either a methyl methacrylate or a polypropylene polymer, panels 30 and 32, drive end flange 2G and spur gear 18 are desirably fabricated from the same material. Thus, a uniformly and highly chemically resistant structure is provided.

From the descriptions thus far given, it is apparent that, during the electroplating operation, the barrel 10 is revolved slowly with its load of parts immersed in the plating solution; and in compliance with customary procedures applying to button-type electroplating barrels, the barrel y10 is only partially immersed in the solution. Electric current passes through the arm 40 to the trunnion 46 and from thence to the spider 60 into the bars 72 andl the button contacts 88. The button contacts touch the parts during cylinder rotation as the parts tumble from -one set of contacts to another.

It is also to be noted from the foregoing descriptions that the barrel is constructed to provide a fluid-tight or leakproof path for the electrical current. Accordingly, the problem of plating action taking place on the electrical supply elements exposed to leakage of the plating solutions is substantially avoided.

Furthermore, in the specific embodiment'wherein a methyl methacrylate polymer is used as the primary material of construction, it will become apparent that visual observation of the parts being plated is afforded. In addition, the economics inherent in the use of the methyl methacrylate polymers accrue.

It is to be pointed out that the specific examples herein shown .and described are illustrative only. Various changes in structure will, no doubt, occur to those skilled in the art; and these changes are to be understood as forming a part of this invention insofar as they fall within the spirit and scope of the appended claims.

The invention is claimed as follows:

1. In an electroplating barrel adapted to be rotated while immersed in an electroplating bat-h, the combination comprising: a pair of electrically insulative end flanges arranged to be rotated in spaced relationship', one of said flanges being Iformed with a recess adapted to receive an electrically` conductive spider, said spider being connectable to a source of power, said recess Ibeing closed by means of a plate sealed over said spider with an adhesive; a plurality of rib means extending between said iianges in peripheral locations, each of said rib means including an elongated electrically insulative member having a longitudinal groove therein, an electrically conductive bar electrically connected to said spider and received in said groove, and a plate member closing said groove by being sealed over said bar using an adhesive; a plurality of perforated panels fastened between adjacent rib means; and electrically conductive contact means including connection means extending radially through each of said rib means in substantially fluid-tight relationship to engage said conductive bar, so constructed and arranged that the structure is resistant to electroplating solutions and provides a substantially fluid-tight electrical path to -the contents of said barrel, wherein said .grooved member, said end flanges, said plate an'd said plate member are fabricated from a methyl methacrylate polymer and wherein said adhesive is a solvent solution of said polymer.

2. In an electroplating barrel adapted to be rotated while immersed in an electroplating bath, the combination comprising: a pair of electrically insulative end flanges arranged to be rotated in spaced relationship, one of said flanges being lformed with a recess adapted toreceive an electrically conductive spider, said spider being connectable to a source of power, said recess being closed by means of a plate sealed over said spider with an adliesive; a plurality of rib means extending between said flanges in peripheral locations, each of said rib means including an elongated electrically insulative member having a longitudinal groove therein, an electrically conductive bar electrically connected to said spider and received in said groove, and a plate member closing said groove by being sealed over said'bar using an adhesive; a plurality of perforated panels Ifastened between adjacent rib means; and electrically conductive contact means including connectionmeans extending radially through each of said rib means in substantially fluid-tight relationship to engage said conductive bar, so constructed and arranged that the structure is resistant to electroplating solutions and provides a substantially fluid-tight electrical path to the contents of said barrel, wherein said .grooved member, said end flanges, said plate and said plate member are fabricated from hard rubber.

3. In an electroplating'barrel adapted to be rotated while immersed in lau electroplating bath, -the combination comprising: a pair of electrically insulative end anges arranged to be rotated in spaced relationship, oneof said flanges being formed with a recess adapted to receive 'an electrically conductive spider, said spider being connectable to a source of power, said recess being closed by means of a plate sealed over said spider; a plurality of rib means extending between said anges in peripheral locations, each of said rib means including an elongated electrically insulative member having a longitudinal groove therein, an electrically conductive bar electrically connected to said spider and 4received in said groove, and a plate member sealed in position over said bar and closing said groove; a plurality of perforated panels fastened between adjacent rib means; and electrically conductive contact means including connection means extending radially through each of said rib means in substantially duid-tight relationship to engage said conductive bar, so constructed and arranged that the structure is resistant to electroplating solutions and provides a substantially fluid-tight electrical path to the contents of said barrel, wherein said grooved member, said end flanges, said plate and said plate member are fabricated from polypropylene.

4. In an electroplating barrel adapted to be rotated while immersed in an electroplating bath, the combination comprising: a pair of electrically insulative end flanges arranged to be rotated in spaced relationship, one of said llanges being formed with a recess adapted to receive an electrically conductive spider, said spider being connectable Ito a source of power, said recess being closed by means of a plate sealed over said spider with a fusionA joint between said plate and said recessed flange; a plurality of rib means extending between said flanges in peripheral locations, each of said ri'b means including an elongated electrically insulative member having a longitudinal groove therein, an electrically conductive bar electrically connected to said spider and received in said groove, and a plate member connected to a said rib means with fusion ljoint means therebetween whereby to close the groove thereof; a plurality of perforated pa'nels fastened between adjacent rib means; and electrically conductive contact means including connection means extending radially through each of said rib means in substantially fluid-tight relationship to engage said conductive bar, soconstructed and arranged that the structure is resistant to electroplating solutions and provides a substantially duid-tight electrical path to the contents of said barrel, wherein said .grooved member, said end flanges, said plate and said plate member are fabricated from polypropylene.

5. In an electroplating barrel adapted to be rotated while immersed in an electroplating bath, the combination comprising: a pair of electrically insulative end flanges arranged to be rotated in spaced relationship, one 0f said anges being formed with a recess adapted to receive an electrically conductive spider, said spider being connectable to a source of power, said recess being closed by means of a plate sealed over said spider with an adhesive; a plurality of rib means extending between said flanges in peripheral locations, each of said rib means including an elongated electrically insulative member having a longitudinal grooves therein, an electrically conductive bar electrically connected to said spider and received v in said groove, and a plate member closing said groove by being sealed over said bar using an adhesive; a plurality of perforated panels fastened between adjacent rib means; and electrically conductive contact means including connection means extending radially through each of said rib means in substantially fluid-tight relationship to engage said 'conductive bar, so constructed and arranged that the structure is resistant to electroplating solutions andprovides a substantially fluid-tight electrical path to the contents of said barrel, wherein said grooved member,

said end flanges, said plate and said plate member are fabricated from a methyl methacrylate polymer.

6. In an electroplating barrel adapted to be rotated while immersed in an electroplating bath, the combination comprising: a pair of electrically insulative end flanges arranged to be rotated in spaced relationship; a plurality of rib means extending between saidflanges in peripheral locations, each of said rib means including an elongated electrically insulative member having a longistantially duid-tight electrical path to the contents of said. barrel, wherein said grooved member and said plate member are fabricated from a methyl methacrylate polymer and said adhesive is a solvent solution of said polymer.

7. In an electroplating barrel adapted to be rotated while immersed in an electroplating bath, the combination comprising: a pair of yelectrically insulative end anges arranged to be rotated in spaced relationship; a plurality of rib means extending between said flanges in peripheral locations, each of said rib means including an elongated electrically insulative member having a longitudinal groove therein, an electrically conductive bar connectable to a source of power and received in said groove, and a plate member closing said groove by being sealed over said bar by an adhesive; an-d electrically conductive contact means including connection means extending radially through each `of said rib means in substantially fluid-tight relationship to engage said conductive bar, so constructed and arranged that the structure is resistant to electroplating solutions and provides a substantially uid-tight electrical path to the contents of said barrel, wherein said grooved member and said plate member are fabricated from hard rubber.

8. In an electroplating barrel adapted to be rotated while immersed in an electroplating bath, the combination comprising: a pair of electrically insulative end anges arranged to be rotated in spaced relationship; a plurality of rib means extending between said flangesin peripheral locations, each of said'rib means including an elongated electrically insulative member having a longitudinal groove therein, an electrically conductive bar connectable to a source of power and received in said groove, and a plate member closing said groove by being sealed over said bar; and electrically conductive `Contact means including connection means extending radially through each of said rib means in substantially fluid-tight relationship to engage said conductive bar, so t constructed and arranged that the structure is resistant to electroplating solutions and provides a substantially fluid-tight electrical path to the contents of said barrel, wherein said grooved member and said plate member are fabricated from polypropylene.

9. In an electroplating barrel adapted to be rotated while immersed in an electroplating bath, the combination comprising: a pair of electrically insulative end anges arranged to be rotated in spaced relationship; a plurality of rib means extending between said flanges in peripheral locations, each of Asaid rib means including an elongated electrically insulative member having a longitudinal groove therein, an electrically conductive bar connectable to a source of power and received in said groove, and a plate member closing said groove by being sealed over said bar by a fusion joint; and electrically conductive contact means including connection means extending radially through each of said rib means in substantially fluid-tight relationship to engage said conductive bar, so constructed and arranged that the structure 8 is resistant to electroplating solutions and provides a substantially fluid-tight electrical path to the contents of said barrel, wherein said grooved member and said plate member are fabricated from polypropylene.

16. In an electroplating barrel adapted to be rotated while immersed in an electroplating bath, the combination comprising: a pair of electrically insulative end anges arranged to be rotated in spaced relationship; a plurality of rib means extending between said anges in peripheral locations, each of said rib means including an elongated electrically insulative member having a longitudinal groove therein, an electrically conductive bar connectable to a source of power and received in said groove, and a plate member closing said groove by being sealed over said bar by an adhesive; and electrically conductive contact means including connection means extending radially through each of said rib means in substantially duid-tight relationship to engage said conductive bar, so constructed and arranged that the structure is resistant to electroplating solutions and provides a substantially duid-tight electrical path to the contents of said barrel, whereinl said grooved member and said plate member are fabricated from a methyl methacrylate polymer.

11. In an electroplating barrel adapted to be rotated while partially immersed in an electroplating bath, the combination comprising: a pair of electrically insulated end anges fabricated from a methyl methacrylate polymer and arranged to be rotated in spaced relationship, one of said flanges being formed with a recess adapted to receive an electrically conductive spider, said spider being fabricated from bronze and being connectable to a source of power, said recess being closed by-means of a cooperatively shaped plate fabricated from a methyl methacrylate polymer and sealed over said spider with a solvent solution of said polymer; a plurality of electrically insulative rib means extending between said anges in peripheral locations, each of said rib means including an elongated electrically insulative member fabricated from a methyl methacrylate polymer and having a longitudinal groove therein, an electrically conductive bar fabricated from brass, electrically connected to said spider and received in said groove, and a cooperatively shaped member fabricated from said polymer and closing said groove by being sealed over said bar using-a solvent solution of said polymer; a. plurality of perforated panels fabricated from said polymer and fastened between adjacent rib means; and electrically conductive contact means including connection means extending radially through each of said rib means to be exposed internally of said barrel and being secured in substantially duid-tight relationship and engaging said conductive bar threadedly, so constructed and arranged that the structure is resistant to electroplating solutions and provides a substantially fluid-tight electrical path to the contents of said barrel.

References Cited by the Examiner UNITED STATES PATENTS 1,916,465 7/1933 Dawson 204-213 1,928,949 10/1933 ONeill 204-213 2,284,163 5/1942 OBrien 174-97 X 2,766,201 10/1956 Luther 204--213 2,836,400 5/1958 Jackson 204-213 2,886,505 5/1959 Singleton et al 204-213 2,894,243 7/1959 Hayes 174-88 X 3,153,624 10/1964 Jackson 204--213 3,159,560 12/1964 Belke 204--213 FOREIGN PATENTS 108,493 12/1958 Pakistan.

JOHN H. MACK, Primary Examiner.

A. B, CURTIS, W. VAN SISE, Assistant Examiners. 

1. IN AN ELECTROPLATING BARREL ADAPTED TO BE ROTATED WHILE IMMERSED IN AN ELECTROPLATING BATH, THE COMBINATION COMPRISING: A PAIR OF ELECTRICALLY INSULATIVE END FLANGES ARRANGED TO BE ROTATED IN SPACED RELATIONSHIP, ONE OF SAID FLANGES BEING FORMED WITH A RECESS ADAPTED TO RECEIVE AN ELECTRICALLY CONDUCTIVE SPIDER, SAID SPIDER BEING CONNECTABLE TO A SOURCE OF POWER, SAID RECESS BEING CLOSED BY MEANS OF A PLATE SEALED OVER SAID SPIDER WITH AN ADHESIVE; A PLURALITY OF RIB MEANS EXTENDING BETWEEN SAID FLANGES IN PERIPHERAL LOCATIONS, EACH OF SAID RIB MEANS INCLUDING AN ELONGATED ELECTRICALLY INSULATIVE MEMBER HAVING A LONGITUDINAL GROOVE THEREIN, AN ELECTRICALLY CONDUCTIVE BAR ELECTRICALLY CONNECTED TO SAID SPIDER AND RECEIVED IN SAID GROOVE, AND A PLATE MEMBER CLOSING SAID GROOVE BY BEING SEALED OVER SAID BAR USING 